title: Left ventricular mechanical dispersion by tissue Doppler imaging: a novel approach for identifying high-risk individuals with long QT syndrome.
abstract: OBJECTIVE
  The aim of this study was to investigate whether prolonged and dispersed myocardial contraction duration assessed by tissue Doppler imaging (TDI) may serve as risk markers for cardiac events (documented arrhythmia, syncope, and cardiac arrest) in patients with long QT syndrome (LQTS).
  
  
  RESULTS
  Seventy-three patients with genetically confirmed LQTS (nine double- and 33 single-mutation carriers with previous cardiac events and 31 single-mutation carriers without events) were studied. Myocardial contraction duration was prolonged in each group of LQTS patients compared with 20 healthy controls (P < 0.001). Contraction duration was longer in single-mutation carriers with previous cardiac events compared with those without (0.46 +/- 0.06 vs. 0.40 +/- 0.06 s, P = 0.001). Prolonged contraction duration could better identify cardiac events compared with corrected QT (QTc) interval in single-mutation carriers [area under curve by receiver-operating characteristic analysis 0.77 [95% confidence interval (95% CI) 0.65-0.89] vs. 0.66 (95% CI 0.52-0.79)]. Dispersion of contraction was more pronounced in single-mutation carriers with cardiac events compared with those without (0.048 +/- 0.018 vs. 0.031 +/- 0.019 s, P = 0.001).
  
  
  CONCLUSIONS
  Dispersion of myocardial contraction assessed by TDI was increased in LQTS patients. Prolonged contraction duration was superior to QTc for risk assessment. These new methods can easily be implemented in clinical routine and may improve clinical management of LQTS patients.
authors.affiliation: Department of Cardiology, Rikshospitalet University Hospital, University of Oslo, N-0027 Oslo, Norway.
authors.forename: Kristina Hermann
authors.initials: KH
authors.lastname: Haugaa
authors.forename: Thor
authors.initials: T
authors.lastname: Edvardsen
authors.forename: Trond P
authors.initials: TP
authors.lastname: Leren
authors.forename: Jon Michael
authors.initials: JM
authors.lastname: Gran
authors.forename: Otto A
authors.initials: OA
authors.lastname: Smiseth
authors.forename: Jan P
authors.initials: JP
authors.lastname: Amlie
mesh_terms: D000293:Adolescent; D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000328:Adult; D000368:Aged; D002648:Child; D015150:Echocardiography, Doppler; D006323:Heart Arrest / Q000209:etiology; D006801:Humans; D008133:Long QT Syndrome / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000235:genetics / Q000503:physiopathology; D008875:Middle Aged; D009154:Mutation; D009200:Myocardial Contraction / Q000502:physiology; D018570:Risk Assessment / Q000379:methods; D013575:Syncope / Q000209:etiology; D016277:Ventricular Function, Left; D055815:Young Adult
chemical_list: D000319:Adrenergic beta-Antagonists